Magnetron



ID. PRINZ MAGNETRON Nav. 16, 1937.

Filed July 50, 1955 Z N M T P EH mC Y/ W a ATTORNEY Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE j" Y 2,099,533 7 Y I v MAGNETI'ioN Dietrich Prin' 'Berlin, Germany, assignor to Telefunken' Grtsellscliaft fiir Drahflos Telegraphic m. b. H., Berlin, Germany, a corporation of i Germany Application July so, 193 5 SerialjI-,,N'. 33327 1 In Germany Jlily" 5 1934" 3 Claims.

This invention relates to electron discharge 7 devices for use at very high frequencies and of the type commonly referred to as magnetrons, and the principal object of my invention is to provide an improved form of electrode mount construction for improving the efficiency of such devices,

A type of magnetron tube frequently used contains a straight thermionic cathode surrounded 0 by a pair of concentrically disposed segmental anodes. The two anodes are usually connected to a resonant push-pull circuit tuned to the frequency to be produced. In the operation of the tube, electrons leaving the cathode and movin towards the anode having the higher positive potential applied to it are forced by a magnetic field extending parallel to the cathode to move toward the anode having the lower potential. Only those electrons which reach the anode having the lower potential contribute to the production of oscillations, while the remaining electrons which reach the anode at the higher potential result in energy loss in the formof heat.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended: claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a schematic section transverse to the longitudinal axis of a conventional split anode electron discharge device and-Figure 2 is a schematic section transverse to the longitudinal axis of an electron discharge device embodying my invention.

Figure 1 shows a conventional electron discharge device of the magnetron type having an envelope V containing a straight thermionic cathode is surrounded by two segmental anodes 40 l and 2 in the form of semi-cylinders. In this device there is much likelihood of an electron reaching the anode segment which at the particular moment is at the higher potential. In Figure 1, the anode I is assumed to be at the lower potential, and the anode 2 at the higher potential. An electromagnetic coil M is provided for producing a magnetic field parallel to the cathode. The course of an electron is indicated by the dotted curved line 3 defining a spiral path.

This results in. many of the electrons not reaching the anode at lower potential, thus reducing the efiiciency of the tube.

In accordance with my invention the probability of an electron reaching the anode having the higher potential, is diminished by so positioning the anodes relative to the cathode that the distance between the anodes and the cathode increases in the direction in which'the electrons move from the cathode to the anodes.

Figure 2 shows a tube embodying my invention and having an envelope V containing two semicylindrical anodes l and 2 which are not positioned concentrically of the cathode k, but are displaced laterally with respect to each other, so that the radial distance between the cathode and curved surfaces of the anodes increases in a clockwise direction when looking down at the top ends of cathodes and anodes. An electromagnet M is provided outside the envelope to produce the magnetic field parallel to the cathode. The electron path 3" takes a course similar to that in Figure l terminating, however, as. shown in Figure 2, not on the anode 2 at higher potential, but on anode l at the lower potential. Since an electron following this path assists in the 20 production of oscillations, the result obtained by the structure in accordance with the invention is twofold, first the losses are reduced, and second the energy of oscillation is increased. The result is a notable increase in the efliciency of the 25 tube.

As is obvious, the inventive idea is not limited to the mode of construction represented in Figure 2. Neither is it necessary for instance, that the two anodes have a semi-cylindrical shape, 30 nor that only two anodes be used. Instead the shape of the anode cross section can be varied within the limits set by the idea of the invention, and this idea can as well be applied to tubes with three, four or a greater number of equivalent 35 anodes. To the same extent, no requirement exists of coupling all anodes in the manner previously mentioned, to the useful circuit, and one or several electrodes may serve to simply produce the electric field furnishing the negative resistance.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, 45 it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the, purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:-

1. An electron discharge device for use at high frequencies and having an evacuated envelope containing a straight thermionic cathode for emitting electrons, means for producing an electromagnetic field parallel to and surrounding said cathode for causing an electron leaving said cathode to move in the spiral path away from said cathode, and a plurality of arcuate anodes parallel to said cathode, said anodes being spaced from the cathode a distance increasing in length in the direction of the path traveled by the electron.

2. An electron discharge device for use at high frequencies and having an evacuated envelope having a straight thermionic cathode for emitting electrons, means for producing an electromagnetic field parallelto and surrounding said cathode for causing an electron leaving said cathode to move in the spiral path away from said cathode, and a pair of semi-cylindrical anodes mounted parallel to said cathode, and disimagnetic field parallel to and surrounding said cathode for causing an electron leaving said cathode to move in the spiral path away from said cathode, and a plurality of anodes parallel to said cathode, said anodes being spaced from the oathode a distance increasing in length in the direction of the path traveled by the electron.

DIETRICH PRINZ. 

